https://phys.org/news/2018-10-echos-eta-carinae-nebula.html

As radiation and shocks from stellar flares propagate outward through the interstellar medium they encounter wisps and cloudlets of material that then light up – "echos" of the flaring events themselves. CfA astronomer David James was a member of a team that has been studying light "echoes" from Eta Carinae. The team has previously published its results on echoes seen since 2003, but now reports finding a new echo from careful subtraction of images taken at different epochs. The new echo is somewhat brighter than others they have seen, and is distinct in its character: it fades away more slowly and shows different spectral characteristics.

The scientists analyzed images and spectra of the nebula taken at optical wavelengths with the CTIO Blanco and Magellan Baade and Clay telescopes, and in the infrared with the IRAC camera onboard Spitzer. The spectra reveal for the first time very high expansions speeds in the gas, up to fifty million miles an hour, and evidence of a two-phase eruption which the scientists can trace back to the Great Eruption. They interpret the results to argue for a triple-star system that led to the merger, kicking out the original primary star. (They also detect evidence for prior eruption activity - as much as 600 years before the Great Eruption.) The new scenario differs in several key ways from earlier suggestions, and can more easily explain a wider variety of observations. There is a record of observation of Eta Carinae dating back to John Herschel, with many detailed results over the past decades. If in fact Eta Carinae's eruption really was a triplet merger of this sort, these data offer new insights into how very high mass stars form and evolve in their environments.

                                                            
                                    
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